Structural Safety-Catch Of Reinforced Concrete Member Subjected To Repeated Earthquakes

• Main Author: Omid, Hassanshahi
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: T Technology; TA1-2040 Engineering (General). Civil engineering (General)
• Online Access: http://eprints.usm.my/45713/1/Structural%20Safety-Catch%20Of%20Reinforced%20Concrete%20Member%20Subjected%20To%20Repeated%20Earthquakes.pdf; http://eprints.usm.my/45713/

The primary goal of requirements in seismic design codes is to protect the life and safety of building occupants during severe earthquakes. Meeting this objective requires that the risk of structural collapse be acceptably low. The collapse safety provided by current seismic codes sometimes may be challenging due to possibility of over loading condition (e.g. repeated earthquakes) and improper performance of structural system, which are impossible to predict. The present study overcomes the problem by an innovative concept to achieve a new structural system with quickly recovering post-yield stiffness to apply in a typical cantilever Reinforced Concrete (RC) member that considered as an equivalent Single Degree Of Freedom system (SDOF). This investigation is categorized into three main steps according to the three objectives of the study. First, the effect of various parameters such as post-yielding stiffness ratio and plastic rotation capacity on the seismic collapse response of the equivalent SDOF systems, under repeated earthquakes, is evaluated. It was found that the post-yielding stiffness ratio is the most influential parameter affecting the seismic collapse response of the ductile systems (the equivalent SDOF systems with high plastic rotation capacity) when subjected to repeated earthquakes. Second, a mechanism for achieving the new structural system with quickly recovering lateral post-yield stiffness is developed. The Structural Safety-Catch (SSC) concept is proposed, which provides the potential of utilizing a SSC device (as a secondary system) in the ductile systems (as a primary system) for collapse prevention during repeated earthquakes. The primary purpose of SSC concept is to protect the life and safety of building occupants during severe earthquakes by providing additional time for escape, for the occupants. The SSC device was designed using the mechanical contact method, where a secondary bending stiffness is provided by closing a gap, to install in the primary system when entered into inelastic range of performance. The primary and secondary systems together form the new structural system through the proposed SSC concept which known as the Structure-SSC device (S-SSC) system. Third, a slotted steel circular tube, as a SSC device (or a secondary system), is located in the plastic hinge zone of typical cantilever RC member (as a primary system) to prevent collapse mechanism using the S-SSC system. A comparison is made between the typical cantilever RC member as Original RC (RC-O) member and the same typical cantilever RC member retrofitted by the proposed SSC device (RC-SSC member). The load-deflection response of RC-SSC member revealed recovery of post-yield performance, compared to the RC-O member, which verified the efficiency of the S-SSC system. Furthermore, an internal application of the slotted steel circular tube had the added advantages of protecting the member core, and increased both the post-yield stiffness and the ductility capacities of cantilever RC members at the same time. The plastic hinge was also relocated away from the fixed end (or from the joint) along the member length to where the gap of the inner steel circular tube is formed. These results showed that the seismic collapse capacity of the typical cantilever RC member was improved due to the application of proposed SSC device.